The ADM3491 is a 3.3 V differential line transceiver for RS-485 and RS-422 networks from Analog Devices, in the full-duplex configuration: it has a separate driver (Y/Z outputs) and a separate receiver (A/B inputs), so it can transmit and receive at the same time over a four-wire link. ADM3491ARZ-REEL is the RoHS-compliant ("Z") 14-lead SOIC version on tape and reel. It belongs to the ADM3483/3485/3488/3490/3491 family of low-power 3.3 V transceivers.

Two characteristics define it. First, full duplex: unlike a half-duplex (two-wire) RS-485 part that shares one differential pair for both directions, the ADM3491 keeps transmit and receive on separate pairs, which suits point-to-point and multidrop links that need simultaneous bidirectional traffic. Second, the drivers are slew-rate limited, which reduces EMI and the reflections caused by improperly terminated cables - while still supporting data rates up to 20 Mbps, well above the 10 Mbps of standard RS-485.

The part runs from a single 3.3 V supply drawing about 0.84 mA, presents one unit load so up to 32 transceivers can share the bus, and handles the -7 V to +12 V common-mode range of RS-485. Driver and receiver each have an enable (DE high-active, /RE low-active); with DE low and /RE high the device enters a low-power shutdown (nanoamp supply current). It comes in a 14-lead SOIC.

Note: Values are taken from the Analog Devices ADM3491 datasheet. Confirm every parameter against the latest official documentation before committing a design.

ADM3491ARZ-REEL is supplied in the 14-lead SOIC (narrow-body small outline, ADI outline R-14), with a 1.27 mm lead pitch. "Z" marks the RoHS-compliant lead-free finish and "REEL" the tape-and-reel packing. The same ADM3491 die is also offered in 14-lead PDIP (N-14) and 16-lead TSSOP (RU-16). As a bus transceiver, terminate the differential line at both ends, keep the A/B and Y/Z pairs routed as pairs, and place the supply decoupling close to the VCC pins. Package dimensions and pin-1 orientation are shown below.

📄 Full specifications are detailed in the official Analog Devices ADM3491 datasheet.

The 14-lead SOIC brings out the logic-side control and the two differential pairs of a full-duplex transceiver:

• RO (pin 2): Receiver output (logic side).
• /RE (pin 3): Receiver output enable, active low.
• DE (pin 4): Driver output enable, active high.
• DI (pin 5): Driver input (logic side).
• Y, Z (pins 9, 10): Driver differential outputs (non-inverting / inverting), to the bus.
• A, B (pins 12, 11): Receiver differential inputs (non-inverting / inverting), from the bus.
• VCC (pins 13, 14): 3.3 V supply.
• GND (pins 6, 7): Ground. Pins 1, 8 are NC.

Refer to the package drawing below for the physical pin numbering of the 14-lead SOIC.

The parts below are related ADI 3.3 V RS-485/RS-422 transceivers from the same family, available in our catalog. They are not all drop-in replacements; verify duplex mode, data rate, enables and pinout before substituting.

Selection Tips: Stay with the ADM3491 for full-duplex (four-wire) 3.3 V RS-485 at up to 20 Mbps. The ADM3488 is the closest full-duplex sibling; for two-wire half-duplex buses use the ADM3490/ADM3493/ADM3485/ADM3483. Match duplex mode and data rate to the network topology first.

Analog Devices, Inc. (ADI), headquartered in Wilmington, Massachusetts, USA, is a global leader in high-performance analog, mixed-signal and RF semiconductors, with a long-established line of RS-485/RS-422 and interface transceivers. The ADM3491 belongs to ADI's 3.3 V RS-485 family, combining full-duplex operation, slew-rate-limited drivers and low supply current for robust industrial serial networks.

ADI backs the ADM3491 with full datasheet characterization and application guidance on termination, fail-safe biasing, node loading and layout - the details that determine reliable communication over long multidrop cables.